1. Field of the Invention
Broadly speaking, the present invention relates to novel compounds containing synthetic peptide moieties. More particularly, the invention relates to peptidomimetics of natural substrates for activated protein C (APC), which substrates are promoters of the blood coagulation process. The invention further relates to the use of such compounds in the inhibition of anticoagulation processes and the promotion of coagulation processes in blood.
2. Description of the Related Art
Activated protein C (APC) is a serine protease involved in blood coagulation and fibrinolysis. It can be described as trypsin-like in that it is protease which preferentially hydrolyzes peptide, ester, or amide bonds in which a basic amino acid provides the carbonyl group of the scissile bond. The in vivo specificity of this enzyme is a complex function of a variety of structural factors including binding domains in the protease for specific no acid side chains located on both the amino and carboxyl side of the targeted lysine or arginine residues in the substrate protein. The idea that short peptide substrates can be designed to incorporate enough information to discriminate among various proteases relies on the concept that each active site is comprised of a unique series of side chain binding pockets.
Lawson et al., (J. Biol. Chem. 267: 4834-4843, 1992), which is incorporated herein by reference, discusses the development of a fluorescent substrate [6-(Mes-D-Leu-Gly-Arg)amino-1-(dimethyl)naphthalenesulfonamide which can be used to directly measure the enzymatic activity of factor VIIa in the presence and absence of tissue factor and phospholipid.
Butenas et al., (Biochem. 31:5399-5411, 1992) which is incorporated herein by reference, describes 6-amino-1-naphthalenesulfonamides and 6-peptidylamimo-1-naphthalenesulfonamides useful in the detection of serine proteases involved in coagulation and fibrinolysis.
Butenas et al., (Chemistry, [Lithuanian Academy of Sciences] 182:144-153, 1992) which is incorporated herein by reference describes the synthesis of 6-amino-1-naphthalenesulfonamides and suggests that these compounds may be used as detecting groups in peptide substrates for proteases.
Butenas et al., (Anal. Biochem. 225:231-241, 1995) which is incorporated herein by reference describes various isomers of aminonaphthalenesulfonamides and peptidylaminonapthalenesulfonamides including 6-amino-2-naphthalenesulfonamide and 6-peptidyl-2-aminonaphthalenesulfonamide useful in the detection of APC.
U.S. Pat. No. 5,399,487 discloses compounds of the formula: 
wherein
R1 is hydrogen, lower alkyl, alkenyl, alkynyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, or phenylalkyl;
R2 is hydrogen, alkyl, alkenyl, alkynyl, cycloalkyl, alkylcycloalkyl, cycloalkylalkyl, or phenylalkyl; or
NR1R2 forms a nitrogen heterocycle; and
R3 is hydrogen, an amino acid or a peptide residue.
Those compounds are said to function as substrates in assays for determining proteolytic enzyme activity or as enzyme inhibitors.
The present invention provides compounds of formula I: 
or the pharmaceutically acceptable salts thereof wherein:
R1 is benzyl group or a peptide of the formula 
xe2x80x83wherein
R3 and R4 represents free or protected amino acid side chains, and R5 hydroxy, alkoxy, benzoxy, and amino acid or peptide residue; and
R2 is an amino acid or a peptide residue.
Compounds of formula I provide APC inhibitors having high specificity for this particular enzyme.
The present invention also provides compounds of formula II 
or the pharmaceutically acceptable salts thereof wherein:
R3, R4 and R5 are same as in formula I; and
R6 is 6-aminonaphthalenesulfonamide attached to the peptide group via the sulfonamide nitrogen atom or either a free or protected amino group attached to the peptide group via a terminal nitrogen atom.
Compounds of formula I and II protect coagulation factors VIIa and Xa from the inhibition by tissue factor pathway inhibitor (TFPI). These compounds also enhance thrombin generation rate in a reconstituted in vitro model of blood coagulation.
The invention provides promoters of blood coagulation.
The compounds of formula I and II are highly selective inhibitors of the anticoagulation process in blood. The procoagulant activity is due, in part, to the inhibition of the anticoagulant pathways. Antithrombin III, APC and TFPI regulate blood coagulation in a negative fashion. Compounds of formula I that may be employed as inhibitors of the APC bind to this enzvme with high affinity but are hydrolyzed slowly or not at all. Consequently, the invention provides compounds useful in interfering or inhibiting the anticoagulation process in blood. Additionally. these compounds accelerate prothrombin activation in a reconstituted in vitro model of blood coagulation. As a summary of all three effects, compounds of formula I and II decrease clotting time of normal, factor VIII-deficient, and factor IX-deficient plasmas, as well as of whole blood.